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NFR Wizards Archives: FTP-Data connections?

FTP-Data connections?

fernando_montenegrohp.com
Wed, 10 Nov 1999 11:17:33 -0500

Hi everyone!

I've just come across a curious problem, and I wonder if you guys can help me...

When connecting to a remote FTP server (I've tried ftp.microsoft.com,
ftp.redhat.com and ftp.cdrom.com, among others) from a command-line FTP client
(running on Linux), the standard FTP control connection works fine, but the
data connection (on 20/tcp) never gets established.

The weird thing is that the control connection reports "No route to host" after
it fails to connect back to my client on a high port. No traffic ever reaches
the local LAN or the connecting router.

Passive mode doesn't work either.

This is happening off one particular ISP, who assures me they have no filtering
whatsover installed. When testing off a different ISP, things work out fine
(data connection gets established and transfers work without a glitch).

Can anyone shed any light on what might be causing this? If there was no route
back, the control connection wouldn't be established, would it?

I am wondering if the ISP didn't add a stateful packet filter somewhere up the
route and forgot to mention it to us. Any other ideas?

ObFirewalls: When this finally works, the ISP link on our end will be protected
with a Firewall. Before making by job harder by adding the firewall into the
equation, I'm testing the simple stuff first...

Thanks!

Cheers,
Fernando 

--
Fernando da Silveira Montenegro     Hewlett-Packard Brasil
HP Consulting - Internet Security   Al. Rio Negro, 750 - Alphaville
mailto:fernando_montenegrohp.com   Barueri, SP - Brazil 06454-000
voice: +55-11-7297-4351             #include <disclaimer.h>

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